A new wave scheme for trajectory simulations of stratospheric water vapor

We have developed a new wave scheme particularly aiming to provide better temperature fields with realistic variability for trajectory modeling of dehydration processes in the tropical tropopause layer (TTL). The new scheme includes amplitude-phase interpolation and amplification of waves in reanalysis data. Amplification factors are based on statistical variability differences between reanalysis data and radiosonde observations at four Western Pacific locations during boreal winters for 1997-2013. We show that conventional linear interpolation of temperatures in the vertical coordinate degrades wave amplitudes and variability. Amplitude-phase interpolation in Fourier space greatly mitigates the problem found in linear interpolation. Further, amplifying amplitudes of existing waves in reanalyses results in realistic variability. In addition to improvements in variability, cold point temperatures shift to lower values and tropopause heights get higher. Changes in these indicate that the new approach will reduce uncertainties in simulations of TTL cirrus clouds and stratospheric water vapor.